list.add上的NullPointerException

Question

我在modelData.add(i, es)方法中獲得NullPointerException。我從調試中知道es不是null。我真的很困惑，謝謝。

public class EventTableModel extends AbstractTableModel { 

    //private int rowCount = 0; 
    protected List<EventSeat> modelData; 
    private static final int COLUMN_COUNT = 3; 
    private Event e; 
    Event j = GUIpos.m; 
    int i = 1; 

public EventTableModel(Event e) { 
    this.e = e; 
    try { 
     System.out.println(modelData); 
     for (EventSeat es : e.getEventSeats()) { 
      modelData.add(i, es); 
      i++; 
     } 
    } catch (DataException ex) { 
     Logger.getLogger(EventTableModel.class.getName()).log(Level.SEVERE, null, ex); 
    } 

} 

Answer 1

您需要初始化列表以獲取NullPointerException。

protected List<EventSeat> modelData = new ArrayList<EventSeat>(); 

Answer 2

嘗試

protected List<EventSeat> modelData = new ArrayList<EventSeat>(); 

Answer 3

在第一次看，好像modelData尚未實例。我會實例化modelData這樣的：

protected List<EventSeat> modelData = new ArrayList<EventSeat>(); 

僅供參考。在Java 7中會出現一個新的語法，你可以使用 - someObject?.doSomething();